Here's what rhymes with syntactical.

Consider these alternatives

morphological / logical phonological / logical orthographic / traffic morphemes / sense predicates / states typological / logical prosodic / logic notational / educational similarity / therapy derivational / educational stylistic / characteristic phonetic / magnetic morphophonological / logical orthographical / classical aspectual / intellectual wordplay / they lexemes / sense imprecision / given vocalizations / relations morphophonemic / phonemic illogic / logic